The best mic mod platform

Sunday, July 7th, 2013 | by

MXL SMT PCBThree months ago I lamented the demise of the most popular mic mod platform, when the MCA SP-1 began shipping with a surface-mount circuit board. I spent many weeks since then researching inexpensive condenser mics — and buying a closet full of them from Ebay — and now I’m ready to name the heir to the SP-1’s throne.

MXL no longer has a monopoly on mics for upgrading. In fact, I can’t recommend their products for the DIY crowd at all. But there remains one mic that deserves your attention, a mic that makes a fantastic mod platform.

What makes a good mod platform?

There are prerequisites. The mic’s circuit must be familiar. The mic must respond well to upgrades. And finally, the mic must be inexpensive: less than $80 surely, and better still to be $50-$60.

The SP-1 had all these qualities. Its circuit was based on a design by Schoeps, which when properly built and optimized can deliver remarkably high fidelity. But its small-diaphragm capsule was hit-or-miss; some sounded decent, and some not so much, because in a $45 microphone there’s not much budget available for enforcing high tolerances in manufacturing, nor for quality testing after the fact.

The new best

After some searching, I found a mic that shares all of the qualities that made the SP-1 such a great mod platform. It is actually better, in a couple respects.

The new mic uses the same Schoeps-derived circuit as the SP-1. But it adds a useful high-pass filter switch, so you can reduce rumble or proximity effect right at the microphone.

This circuit is inspired. It is simple, efficient, and as noted previously, capable of remarkably high fidelity. You’ll need to tune it to get the most out of it, though. But that’s what makes it so great for DIY upgrades: you’ll really hear the improvement.

Unlike the SP-1, this mic has a large-diaphragm capsule. It tends towards a bright and peaky response, true enough, but if a replacement capsule isn’t in the budget, you can tune the circuit to tame the capsule’s response.

So, if you’re looking for an entry-level mic to modify, I give you: the CAD Audio GXL2200CAD GXL2200.

It’s a really nice mic for the $60* you’ll pay for it. But it gets even better if you roll up your sleeves, fire up the soldering iron, and hot-rod it.

*As of this writing, both Front End Audio and Amazon have the mic on sale for $60; see GXL220 sale pricing.

… and its many siblings

GXL2200 PCBThe circuit board set found in the GXL 2200 turns up in a number of other mics that are equally modifiable. If the 2200 isn’t doing it for you for whatever reason, try the Nady SCM-800, Nady SCM-900, Apex 435, and probably the t.bone SC400 too. I can’t guarantee that all these mics are identical, because at least some of them are known to have changed circuits entirely during their lifetime (hello, transformer-coupled SCM-900!). Compare your mic to the GXL2200 PCB photos published here to ensure compatibility.

How to modify the CAD GXL2200

If you search the various audio forums, you’ll see dozens of suggestions for Schoeps circuit mods. Common suggestions include:

  • Replace the input coupling capacitor (which is on the back of the audio circuit board, soldered to the standoff pins where the capsule wires attach) with a 1000pF polystyrene or silver mica unit. This will decrease distortion quite a bit.
  • Upgrade the audio filter capacitors to film types. Do the two caps on either side of the HPF switch first.
  • Swap the stock capsule for any of these large-diaphragm microphone capsules.

Or if you don’t relish the idea of spending hours poring over contradictory and incomplete mod recipes on the forums, you can put your hands on an expert-designed mod kit that overhauls the microphone entirely — both the audio circuit and the DC power circuit. There’s no guesswork, no need to reconcile conflicting advice, and no need to source exotic parts from six different suppliers in three countries. Check out the new “Pushbutton Filter” mod kit for CAD GXL2200, currently on sale.

[Full disclosure: this kit was my idea. Because, once I’d found the perfect mic mod platform, I made damn sure there would be a mod kit to match it.]

Lightning never strikes twice

If history is any guide, then by the time you read this this article, surface-mount versions of the GXL2200 will be arriving at your favorite gear discounter. But no, not this time! I checked with CAD last week and learned that they have no plans to migrate to surface-mount boards for the GXL mics. We can’t predict the future, but for now any GXL2200 you find should be perfect for homebrewed upgrades.

But who cares about DIY?!

DIY gear mods are not for everyone, I will admit. If you can afford a locker full of vintage Neumann, AKG, and Telefunken microphones, by all means do so!

On the other hand, if you have a bit of downtime between sessions, and some cheap entry-level gear that isn’t otherwise getting used, then DIY upgrades make so much sense. For a relatively small investment you can turn out some world-class gear. I know; I’ve done it.

Posted in DIY, Microphones | 6 Comments »

6 Responses to “The best mic mod platform”

  1. Euclio

    August 20th, 2013 at 4:55 am

    Hi Matthew, as I see, at most dealers, the “black pearl” special anniversary edition of this microphone the CAD GXL2200BP is available at this time. Can you, please, confirm that this is the same microphone internally, only the cosmetic finish is different.

    Thank you in advance for your help.

  2. Anthony Latva

    October 15th, 2013 at 4:05 pm

    Thanks for the great article!

    One question. Can anyone confirm that this mod is doable to t.bone SC 400? It would be a good option since I will be ordering some stuff from Thomann soon.

  3. matthew mcglynn

    October 15th, 2013 at 4:15 pm

    @Anthony, if your SC 400 circuit board looks identical to the GXL2200, then the mod kit linked above will work well. See PCB photos in the RecordingHacks mic database, e.g.:

  4. andon

    July 30th, 2014 at 7:43 am

    Where can I learn on the web to put this mod kit together (video instructions would be best). I’m a newbie, please help?

  5. Szegedin

    November 24th, 2014 at 8:53 pm

    I’m wondering whether the pcb on the GXL2200 is the same as the one on it’s small diaphragm sister the gxl1200…? Any idea? Would like to do a mod to that one.

  6. Geert van Dijk

    October 5th, 2016 at 6:07 am

    I’ve just got the SC-400 by Thomann, which has the same PCB. I’m going to try and replace the input coupling capacitor first, with a 1000pF silver mica one, like you specified. Mainly to test my soldering skills before doing some more serious mods.
    I have just one question; does the voltage rating on these things matter? I have absolutely zero experience in this and don’t know if it influences anything, or if it’s just a matter of how much it can maximally handle.
    I’ve got a couple of 1000v rated 1000pF silver mica units ready, will one of those do?

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